Below are very safe supplements shown to improve insulin sensitivity
-Vitamin D
-Magnesium
-Chromium
-Cinnamon
-Apple cider vinegar
-Fish oil
-Tumeric
-Zinc
-Exercise/muscle contraction upregulates Glucose transporters in an insulin-independent fashion lowering blood glucose!

Personally, I believe excessive positive energy balance (obesity+sedentary), coupled with a genetic predisposition towards ectopic fat deposition and beta cell susceptibility for lipotoxicity, are major factors leading to insulin resistance.

VLDL — pancreas fat
Hypertrophic adipose tissue — lpl modification — higher residence time
Hypertrophic adipose tissue — Lipolysis — liver beta oxidation — Gluconeogensis
GWAS — susceptible to pancreas damage — T2D
Subcutaneous hypertrophy — macrophage release Lipolysis THF-alpha & IL-6 — Lipolysis — DAG in liver — PKC epsilon in liver

(PKC theta in muscle)